So, since I brought it up, a little more information about soil pH.
The alkaline soil is quite easy to recognize, it’s usually clay, heavy, and out in the open, away from any large trees and shrubs, whose annual leaf drop helps acidify the soil. It tends to dry out on the surface, but deep down it keeps moisture better than other soil types, and plants who had time to develop a good root system thrive in it. It is usually found in the open plains and arid areas.
The acidic soil usually goes hand in hand with woodland settings, it is loose and crumbly, smells like humus and would dry out very quickly if it weren’t usually found in areas with heavy rainfall, which tends to wash out some of the elements in the soil and increase its acidity.
The ideal soil, the Holy Grail of gardening, seldom found in nature, is deep black, rich and buttery, holds on to its water, is not as heavy as clay, but still gives the roots some substance to sink into, and it is pH neutral. It is very fertile, and usually doesn’t happen all by itself, but as a result of adding natural fertilizers, tilling nitrogen rich crops back into the soil and regular turning.
See, now I don’t have to test my soil to know that it is alkaline: the hellebores, yarrows, lilacs, delphiniums, purple cone flowers, geraniums, sedums, magnolia and phlox are all proof of that. I just wish I did a soil test before I bothered planting astilbe, lupines and azaleas.
Who loves acidic soils, beside the three plants I just mentioned? Rhododendrons, holly, gardenias and camellias.
What grows in pH neutral soils? Mostly anything that doesn’t require a very acidic or alkaline medium. That means almost all vegetables, except for the brassicas, which don’t like sour soils, and herbs, although the latter tend to favor alkaline soils too, true to the conditions of their native habitat. As you may have guessed already, by their even distribution in acidic and alkaline gardens alike, tomatoes, peppers, cucumbers and squashes don’t much care one way or another, as long as they are well fed.
Hydrangeas are the classic acid test for the plant world: as we know, they turn blue in acidic soils an pink in alkaline ones. This makes for an interesting gardening challenge, but unfortunately I never managed to keep mine alive. In neutral soil their flowers stay greenish white.
Most plants can tolerate a deviation from the soil acidity they are accustomed to, but if you have a really acidic soil, don’t try lilacs or grapevine. They won’t thrive, no matter what you do.

Author's Bio: 

Main Areas: Garden Writing; Sustainable Gardening; Homegrown Harvest
Published Books: “Terra Two”; “Generations”; "The Plant - A Steampunk Story"; "Letters to Lelia"; "Fair"; "Door Number Eight"
Career Focus: Author; Consummate Gardener;
Affiliation: All Year Garden; The Weekly Gardener; Francis Rosenfeld's Blog

I started blogging in 2010, to share the joy of growing all things green and the beauty of the garden through the seasons. Two garden blogs were born: allyeargarden.com and theweeklygardener.com, a periodical that followed it one year later. I wanted to assemble an informal compendium of the things I learned from my grandfather, wonderful books, educational websites, and my own experience, in the hope that other people might use it in their own gardening practice.